This invention is in the field of vehicles for road and rail use and in particular the suspension of such vehicles.
Vehicles adapted for road and rail use are well known. Commonly a truck or highway tractor will include conventional rubber tired wheels for road use, and a set of rail wheels which allow the truck to travel on railway lines. Short-line railways have made such convertible highway tractors, or road/rail power units, popular for economically pulling small numbers of rail cars on low volume rail lines. Conventional railways also use them for shunting, maintenance, and like jobs where large locomotives are not required and are uneconomical. The road/rail power units are more versatile than locomotives as they allow for direct movement between rail lines on roads. Towed vehicles are also known that convert from road to rail modes.
The suspension of such vehicles typically includes some apparatus to raise and lower the rail wheels, and may further include mechanisms for raising at least some road wheels. It is necessary that those wheels of either kind that are not being used are removed from the road or rail so as not to interfere with the operation of the vehicle in the particular mode it is operating in.
Air bag suspensions are popular to support the vehicle on the rail wheels in rail mode as they allow the desired degree of movement to provide a smooth ride. Some give is desired to cushion the vehicle from variations in the track, such as uneven joints between rails. Air bags are preferred over springs as they can be collapsed to allow the rail wheels to be raised when the vehicle converts to road mode. Typically an actuator such as a hydraulic cylinder is used to move the rail wheels up into road mode and down into rail mode. The hydraulic cylinder typically extends or retracts to move the rail wheels down and then the air bag is inflated between the rail wheel and the vehicle frame to support the vehicle with adjacent road wheels raised above the rails. Pressure is then released from the hydraulic cylinder so that same floats, allowing the vehicle to move up and down with respect to the rail wheels on the cushion provided by the air bag.
Typically to convert to road mode, the air pressure in the air bag is released so that the vehicle moves down to rest on the adjacent road wheels. Some of the road wheels might also be raised when moving into rail mode. In that case, those road wheels are typically first lowered before the air pressure in the air bag is released. When the air pressure is released, the hydraulic cylinder is then reversed to raise the rail wheels into the raised road mode position, wherein the air bag is collapsed. A chain or the like is used to secure the rail wheels in the raised road mode position.
A problem with the air bag suspension is that the air bag can fail, allowing the vehicle to drop. The adjacent road wheels may then contact the rail or ties, causing damage to the vehicle or rail bed, or even derailing the vehicle.
It is the object of the present invention to provide an air bag suspension apparatus for mounting a rail wheel to a convertible road/rail vehicle that prevents adjacent road wheels of the vehicle from contacting the rails while allowing the suspension to cushion the vehicle while traveling on a set of rails in rail mode.
It is a further object of the invention to provide such an apparatus that also locks the rail wheels in a raised position for vehicle travel on a road in road mode.
It is a further object of the invention to provide such an apparatus in kit form that can be attached to existing road/rail vehicles.
The invention provides, in one aspect, for use with a road/rail vehicle, the vehicle convertible from a road mode for traveling on a road, to a rail mode for traveling on rails, an apparatus for mounting a rail wheel to the vehicle. The apparatus comprises an air bag and a source of pressurized fluid operatively connected to the air bag to supply pressurized fluid to the air bag such that the air bag bears against the rail wheel and against the vehicle frame such that the vehicle frame is supported on the rail wheel by the air bag and such that the vehicle frame can move up and down with respect to the rail wheel in response to motion of the vehicle along a set of rails. A control is operative to release pressurized fluid from the air bag. An actuator is operatively connected to the vehicle frame and to the rail wheel, the actuator operative to selectively move the rail wheel from a raised road mode position to a lowered rail mode position. A stop mechanism is attached to the vehicle frame and to the rail wheel and is operative to allow the vehicle frame to move down with respect to the rail wheel only to a stopped position; and wherein adjacent road wheels of the vehicle are above the rails in the stopped position.
The invention provides, in a second aspect, a kit for use with a road/rail vehicle, the vehicle convertible from a road mode for traveling on a road, to a rail mode for traveling on rails, the vehicle when in rail mode supported on a rail wheel by an air bag, the vehicle including a source of pressurized fluid operatively connected to the air bag to supply pressurized fluid to the air bag such that the air bag bears against the rail wheel and against the vehicle frame and such that the vehicle frame can move up and down with respect to the rail wheel in response to motion of the vehicle along a set of rails, the vehicle further including a control to release the pressurized fluid from the air bag and an actuator operatively connected to the vehicle frame and to the rail wheel, the actuator operative to selectively move the rail wheel from a raised road mode position to a lowered rail mode position. The kit comprises a stop mechanism attachable to the vehicle frame and to the rail wheel, the stop mechanism operative to allow the vehicle frame to move down with respect to the rail wheel only to a stopped position wherein adjacent road wheels of the vehicle are above the rails.
The apparatus allows the vehicle to move up and down with respect to the rail wheels so that the suspension can cushion the vehicle, while preventing the adjacent road wheels from coming into contact with the rails or rail bed should the air bag fail. The apparatus can also readily incorporate a lock to secure the rail wheels in the raised road mode position for travel on the road.